Sodium carbonate is soda ash, or washing soda (old Arm and Hammer product). Typcially found as pentahydrate, but Benedict's calls for anhydrous, so need to adjust. Copper sulfate is an algacide for swimming pools. Potassium sodium tartrate crystals can be grown by heating and then cooling a solution of cream of tartar (a common spice) and washing soda (sodium carbonate). Citrate is common and can be sodium or potassium for Benedicts. Potassium thiocyanate and potassium ferricyanide are available as photography supplies.
Reagents used for testing foodstuffs
Biuret reagent
This is used to test for the presence of protein. There are two recipes the first consists of two reagents Biuret A and Biuret B.
The reagent is made up by first dissolving 173g of sodium citrate and 100g of anhydroussodium carbonate in about 600ml of distilled water. Then 17.3g copper (II) sulfate · 5H2O is dissolved in about 100ml of distilled water. The two solutions are then mixed together and when cool are made up to 1L with distilled water.
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Reagents used for testing foodstuffs
Biuret reagentThis is used to test for the presence of protein. There are two recipes the first consists of two reagents Biuret A and Biuret B.
- A is 0.1M sodium hydroxide or potassium hydroxide the bottle should be labelled CORROSIVE.
- B is 0.01M copper (II) sulfate solution
For the second (Quantitative) recipe, in about 600mL of distilled water, dissolve in order 3g of copper (II) sulfate · 5H2O, 5g of potassium iodide, 9g of potassium sodium tartrate.4H2O, and 8g of sodium hydroxide. Make the dissolved solids to 1 litre. Label the solution IRRITANTBenedict's reagent is used to test for reducing sugars. It has two recipes. Benedict's qualitative and Benedict's quantitative.
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Benedict's Qualitative Reagent
The reagent is made up by first dissolving 173g of sodium citrate and 100g of anhydrous sodium carbonate in about 600ml of distilled water. Then 17.3g copper (II) sulfate · 5H2O is dissolved in about 100ml of distilled water. The two solutions are then mixed together and when cool are made up to 1L with distilled water.[edit]
Benedict's Quantitative Reagent
In about 600ml of hot water dissolve- 200g of sodium citrate
- 75g sodium carbonate
- 125g potassium thiocyanate
In about 100ml of water dissolve- 18g of copper (II) sulfate · 5H2O
When the solutions have cooled, mix them together stirring constantly. Add- 5ml of 5% potassium ferrocyanide then make up to 1L.
[edit]Iodine Solution
- Iodine solution is used to test for starch.
Recipes vary but 1g of iodine plus 1g of potassium iodide in 100mL water is suitable. Dissolve the iodide then the iodine.